#to_s should give back the inspection view

I was doing some debugging, and ran across something confusing:

```ruby
puts params # {}
puts params[:name] # "Aidan"
# wtf??
```

After some banging of my head against the wall, I discovered that `params` was a `TaintedHash`, and that I had merely run myself in circles.  Hopefully this will spare others the same pain in the future.

```ruby
puts params # #<TaintedHash:2185660760 @hash={"a"=>1, "b"=>2, "c"=>{"name"=>"bob"}} @exposed=[]>
```